(a) Field of the Invention
The present invention relates to an electronic device in which an extension portion projects from a printed board disposed in a housing, and a plurality of leader patterns are provided on the extension portion, and in particular, relates to an attachment structure for a mounting the electronic device on to a mother board.
(b) Description of Background Art
In an electronic device such as a tuner or the like, it is necessary to enclose a printed board in a box-like housing so as to shield the circuit parts mounted on the printed board from unnecessary external signals, or so as to shield circuits near the electronic device from signals, noise, or the like generated by the circuit parts of the electronic device.
FIG. 10 is a front view showing an example of a conventional electronic device in the background art. The electronic device shown in FIG. 10 is commonly referred to as a vertical type electronic device. The electronic device is, for example, a tuner, and is constituted by a box-like housing 10 and a printed board 11 received in the housing 10. An extension portion 12 projecting downward from the housing 10 is provided on the printed board 11 so as to extend therefrom. A plurality of leader patterns 13 are provided in parallel on the extension portion 12, while metal terminals 14 for input/output are fixed to the leader patterns 13 by caulking, respectively. In addition, a plurality of leg pieces 15 extending downward are provided on the housing 10 so as to project therefrom. The leg pieces 15 are located on opposite sides of the extension portion 12.
FIG. 11 is a front view showing another example of a conventional electronic device in the background art. This electronic device is commonly referred to as a horizontal type electronic device, and has a basic structure that is similar to that of the vertical type shown in FIG. 10. However, in this horizontal type electronic device, an extension portion 22 projects laterally from a housing 20, while metal terminals 24, fixed to respective leader patterns 23 by caulking, are bent downward at right angles.
The vertical type and horizontal type electronic device configured as described above are often mounted on a set-side mother board 16. In particular, the respective metal terminals 14 and 24 and the respective leg pieces 15 and 25 are each inserted into insertion holes formed in the mother board 16. Where the housing 10 is retained on the mother board 16 by the respective leg pieces 15 and 25, lands formed on the back surface of the mother board 16 and the respective metal terminals 14 and 24 are soldered by applying jet solder (flow-dip solder).
However, in the aforementioned conventional electronic devices, the metal terminals 14, 24 are fixed by caulking respectively to the plurality of leader patterns 13, 23 provided in parallel on the extension portion 12, 22. Accordingly, there is a problem in that the cost of the individual parts, or the cost of assembling these parts, increases the cost of manufacturing these electronic devices. In addition, there is a problem that the metal terminals 14, 24 are apt to be deformed when they are mounted onto the mother board 16, or are deformed in transit before they are mounted on to the mother board 16.
Moreover, in the case of the horizontal type electronic device shown in FIG. 11, the total length of each of the metal terminals 24 is longer than that in the case of the vertical type electronic device shown in FIG. 10. Therefore, the likelihood that the metal terminals 24 of the horizontal type electronic device will become deformed is significantly increased. In addition, the step of bending the metal terminals 24 at right angles by use of a jig is required after the metal terminals 24 are fixed to the leader patterns 23. It is therefore necessary to strictly control the bending accuracy of the metal terminals 24. This bending operation likewise increases the cost of manufacturing these devices.
It is an object of the present invention to provide an electronic device in which conventional type metal terminals are omitted so that the manufacturing cost can be reduced. It is another object of the present invention to provide an attachment structure which permits an electronic device to be mounted on a mother board easily and surely.
According to a first aspect of the present invention, an electronic device comprises a plurality of leader patterns and penetration portions penetrating the leader patterns are provided on an extension portion of a printed board projecting from a housing. When such an electronic device is to be mounted on a mother board, the extension portion is inserted into an insertion hole in the mother board so as to project out from the back surface of the mother board. The respective leader patterns of the extension portion and respective lands of the mother board are then soldered to each other by the application of jet solder. The jet solder is applied to the extension portion so as pass through the penetration portions. Thus, the amount of jet solder that remains between adjacent leader patterns is greatly reduced so that generation of solder bridges can be avoided. This aspect of the present invention is particularly suited to a vertical type electronic device.
According to another aspect of the present invention, a plurality of metal terminals are provided erectly on the surface of the mother board. The metal terminals of the mother board are then inserted into the respective penetration portions of the extension portion of the electronic device, and the respective leader patterns of the extension portion and the respective metal -terminals of the mother board are soldered to each other. This aspect of the present invention is particularly suited to a horizontal type electronic device.